In vitro Conjugation between Bacteria Isolated from Acute Pharyngitis and Others from Buccal Cavity Wakas S Mahmood *, Waad M Raouf *, Muhammed S Allawi **
Background: Bacteriological diagnosis of pharyngitis is complicated by the fact that the mouth and pharynx contains a heavy, mixed, normal flora of aerobic and anaerobic bacteria. The normal flora generally outnumbers the pathogens and the role of the laboratory is to distinguish between the commensals and the pathogens.
Objectives: To isolate and identify the aerobic bacterial causes of pharyngitis and that colonize the buccal cavity, and determine the antibiotic resistance.
Methods: Many patients visited the ENT outpatient clinic at Tikrit Teaching Hospital in Tikrit city with acute pharyngitis infection from 12/12/2008 to 22/2/2009. Throat and buccal cavity swabs were collected from one hundred twenty two samples by a physician from each patient that was only infected by acute pharyngitis. After culture on sheep blood agar plate, only bacterial etiology (positive culture result) cases were selected, then swabs were cultured for identification.
Results: There were different types of bacteria isolated from infected throats in this study. The results showed that Streptococcus pyogenes was the most commonly isolated bacteria (37.7%), followed by Staphylococcus aureus (33.6%).While other bacteria came in lesser frequencies. Whereas buccal cavity bacterial isolates showed that Viridans Streptococci were most commonly isolated bacteria (71.3%), then coagulase-negative Staphylococci (21.3%), Pseudomonas aeruginosa (4.1%), and Proteus mirabilis (3.3%). The results of antibiotic sensitivity after curing showed that cured isolates of Pseudomonas aeruginosa and Staphylococcus aureus lost their resistance to Cefotaxime, while cured isolates of Proteus mirabilis lost their resistance to Chloramphenicol, and same for Citrobacter freundii to amoxicillin after curing. Conjugation experiments were done for six isolates. Their resistance to antibiotics and production of virulence factor were changed after curing as donor isolates with the standard strain E.coli HB 101 prepared in university labs. That not harbor any plasmid which have a chromosomal resistance to Tetracycline and not able to produce all studied virulence factors as recipient strain. The results showed that just one isolate of Proteus mirabilis was able to transfer its resistance to Chloramphenicol to the recipient bacteria.
Conclusion: This proved that Chloramphenicol resistance gene was carried on conjugative plasmid and proved the results of curing experiment. Other isolates have failed to transfer their resistance for any antibiotics in conjugation experiments, because their genes may be carried on non-conjugative plasmids.
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